1. Field of the Invention
This invention relates to flash devices, photographic apparatuses using the same, or both, and more particularly to flash units which control the amount of light, photographic apparatuses having automatic focus adjusting devices coupled with such flash units, or both.
2. Description of the Prior Art
Recently, a large number of auto-focus cameras have been developed and been made commercially available. These cameras generally include so-called focus locking devices which are designed to operate on a very narrow target area. When a photographer aims at a subject such as two persons standing side by side at an appreciable distance, the rangefinder spot on the focusing screen may lie between the images of the two persons. Composed in this way, when the auto-focus device is released, the camera focuses not on the two persons which are the subject of principle interest, but on the background. To prevent this, the focus locking device permits preliminary framing with the rangefinder spot directed on the subject of principle interest.
The use of such focus locking devices provides reliability in setting the automatic focus adjustment to the subject of principle interest no matter what position that subject takes in the picture frame.
At the same time, flash units exist which include light control devices that control the amount of light in a flash. Such controls integrate the amount of light reflected from an object to a prescribed level, and upon attaining this level terminate the flash.
Such a flash may be combined with an auto-focus camera. In that case, after a focus locking operation with the subject of principle interest toward the corner of the format, the camera takes the picture with flash illumination. However, the subject of principle interest may not then be positioned in front of the camera. Hence, the amount of light reflected from the subject of principle interest may be decreased and the flash unit's light control device may respond mainly to light reflected from the background. This may result in an overexposed photograph of the subject.
On the other hand, without the use of the focus locking device the subject of principle interest is necessarily positioned at the front and permits the light control to control the light in the flash to otain a proper flash exposure.